The present invention is directed to an expeditious and economical method for making a poured-in-place concrete floor with an integrated decorative aggregate surface. The process results in a terrazzo like appearance at a much lower cost than terrazzo flooring.
It is a common practice in the commercial construction industry to make floors from poured concrete. These floors are generally poured at one time as a monolithic slab potentially covering small or large areas—areas that can approach or exceed 50,000 square feet in some instances. The general process is to pour ready-mix concrete into a formed area, compact and generally grade the concrete with a screed and then level it. Steel reinforcement mesh or bars may be be used in the case where the anticipated load exceeds the tensile strength of the concrete at a given thickness. During the pouring a guide or straightedge may be moved back and forth across the top of the forms to “screed,” or level, the freshly placed concrete. Immediately after leveling, the concrete is generally smoothed with the use of a “bull float”. This presses the existing aggregate into the concrete and brings a rich mixture of fine cement paste to the surface along with water. After the concrete has been leveled and bull floated and all the surface water and sheen has disappeared, the surface of the cement is then typically smoothed using either a powered or hand float. For a coarser, nonskid finish, the surface may be textured using a stiff-bristled brush.
Concrete is a cementitious building material created by combining a mineral filler such as sand and gravel or similar aggregate with a binding agent, such as Portland cement, and water. In the pouring of floors cement mixtures are classified into three groups as a function of the ratio of sand and coarse aggregate as they relate to one part of cement by weight or volume. For example a classification of rich would contain—1 part cement, 2 parts sand, 3 parts coarse aggregate, whereas a classification lean would be made up of—1 part cement, 3 parts sand, 6 parts coarse aggregate. In the pouring of a typical floor a standard mix is used—1 part cement, 2 parts sand, 4 parts coarse aggregate. The volume of water is adjusted so as to make the mixture workable while keeping in mind Abrams' law stating that with a given concrete composition and environment factors, the concrete strength is inversely related to the ratio of water to cement whereby low water-to-cement ratios produce higher strengths.
While concrete floors produce a sturdy and durable floor, an additional surface treatment is often required to enhance the appearance and surface texture of the poured floor. A variety of concrete surface coverings and coatings are commonly used in both commercial and residential environments today. These include sealers and paint applications, as well as a plurality of vinyl tile and “sheet” good products placed over the upper surface of the concrete. The use of masonry tile and quarry stone for large scale flooring purposes has had limited acceptance due to associated material and labor costs. The distinct advantages of tile or stone for durability, maintainability and appearance are well known, however, these benefits are often cost prohibitive for large and open spaces.
Attempts have been made to overcome the limitations of the traditional appearance of monolithic cement floors that are poured in place. See for example U.S. Pat. Nos. 4,748,788, 4,281,496 and 4,496,504, all of which are hereby incorporated by reference for their teachings. In these approaches various techniques are employed for enhancing the surface appearance such as the addition of ornamental aggregate and chemical additives, as well as with the use of specialized machinery. In another process disclosed in U.S. Pat. No. 4,496,504 the coarse aggregate of the mixture is exposed on the upper surface of the concrete, in advance of a screed roller, by passing lifter arms through the concrete and thereby concentrating coarse aggregate in the wet concrete towards the surface, along with cement and fine aggregate forming an overlay to the compacted coarse aggregate. While the aforementioned methods produce the desired results they are characterized by a texture that is rustic in appearance lacking in a smooth, reflective and luxurious surface.
A further method to enhance the appearance of a concrete floor is discussed in U.S. Pat. No. 4,281,496, hereby incorporated by reference for its teachings, where the surface finishing process is reliant on the settling and absence of any aggregate in the surface region in order to produce a thin upper layer which is formed substantially of sand and cement. Once cured the surface of the concrete is treated by means of a power grinder in order to remove a thin layer from the concrete and produce a favorable uniform appearance of the surface that is absent of any defects imparted from the prior steps of leveling and compacting.
A terrazzo floor, on the other hand, is produced over the top of a pre-existing base, often concrete, by suspending aggregate chips in either a modified cementitious or a resinous binder and then grinding and sealing the surface. By not being reliant on the common aggregate filler contained within concrete the proportions, size, color, composition, cost and even the shape of the aggregate are controllable variables to effect the desired appearance and color. The composition of the aggregate can take a plurality of forms including man-made materials such as glass, or natural materials such as marble, granite and the like. The advantage of terrazzo over other commonly used surface finishing materials such as tile are a lack of grout lines as well as durability and ease of maintenance.
However advantageous this post-pouring process might be, a concrete floor or other suitable base must have been previously poured in place to provide the required substrate for the terrazzo matrix of materials to be applied thereover. The additional labor and material costs limit terrazzo as an option in many cases, especially in commercial and retail construction where the square footage will often approach or exceed 50,000 square feet.
In any event, there remains an apparent need for a relatively efficient and economical method for forming and finishing the surface of a poured in place concrete floor. Or, more specifically, a method that is integrated with the pouring and curing process, yet provides an aesthetic and durable finish while substantially decreasing the overall cost of labor and materials by eliminating the subsequent application of surface goods over the cured concrete.
In accordance with the present invention there is provided a method for forming a monolithic concrete floor providing for an integrated ornamental surface using decorative aggregate concurrent with the pouring and finishing of a concrete floor.
In accordance with a further aspect of the present invention, there is provided a concrete floor having a smooth surface finish of an integrated decorative aggregate comprising: of a monolithic, poured on site concrete floor unit; and a topical layer of applied aggregate embedded in the floor unit surface before curing, wherein said aggregate is permanently bonded within a top surface layer of said floor unit, and where said top layer is ground to a smooth surface using abrasives to expose the aggregate.
In accordance with another aspect of the present invention, there is provided a method for forming an integrated ornamental surface on a monolithic concrete floor concurrent with the pouring and finishing of the concrete floor, comprising the steps of: preparing and forming the region upon which the monolithic concrete floor is to be poured; contiguously pouring concrete throughout the formed region; floating the concrete to effectively densify the concrete; allowing the concrete to cure to a semi-stiff state; finishing the exposed upper surface of the poured concrete to produce a generally planar surface; disseminating a quantity of non-permeating aggregate over the semi-stiff concrete surface; integrating the particulates of said aggregate into the upper surface of the semi-stiff concrete with a float; allowing the concrete with the integrated aggregate to at least partially cure; grinding the upper surface with the integrated aggregate therein; and polishing the upper surface with the integrated aggregate.
In accordance with a further aspect of the present invention, there is provided to a concrete floor having a smooth upper surface with an impregnated aggregate, comprising: an on site poured monolithic concrete base; and an upper layer, at the top of the concrete base, having aggregate integrated in the upper layer before curing, wherein said aggregate is permanently bonded within the upper layer and where the upper layer has been ground to expose the aggregate as part of a smooth upper surface.
The present invention, as described in greater detail below, produces the unexpected result of reducing overall costs for forming a terrazzo-like surface finish on a poured-in-place concrete floor, thereby providing the benefits of a terrazzo-like floor without the cost.
Other objects and features of the invention will be apparent to those skilled in the art based on the following description.
The present invention will be described in connection with a preferred embodiment, however, it will be understood that there is no intent to limit the invention to the embodiment described. On the contrary, the intent is to cover all alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.